The invention relates to a transport device for transporting an NMR sample to the probe head of an NMR (Nuclear Magnetic Resonance) spectrometer by means of a transport system.
Such a transport device is known, for example, from the company brochure “Z31123 Bruker Sample Transport,” version 002, of Bruker BioSpin AG, dated Nov. 21, 2008 (Reference [1]).
NMR methods are used for analyzing sample compositions or for determining the structure of substances in samples. NMR spectroscopy is an efficient method for instrumental analysis. In these NMR methods, the sample is exposed to a strong static magnetic field B0 in a z-direction, and for this purpose high-frequency electromagnetic pulses orthogonal thereto are irradiated into the sample in the x- or y-direction. This results in interaction with the nuclear spins of the sample material. The temporal development of these nuclear spins of the sample, in turn, generates high-frequency electromagnetic fields which are detected in the NMR apparatus. The detected RF (radio frequency) fields can provide information about the properties of the sample. In particular, the position and intensity of NMR lines allow conclusions to be drawn concerning the chemical bonding properties in the sample.
In NMR spectroscopy of liquids, the sample in a sample tube is brought into the probe head towards the magnetic field lines, and is examined while stationary or during rotation. For the transport and the rotation, a so-called spinner is used which firmly holds the sample tube and which, as a rotor of a turbine arranged above the magnetic center, can be rotated on an air bearing at a moderate frequency (typically 20 Hz).
In NMR spectroscopy of solids, the sample is introduced directly into a rotor in which the sample is transported into the probe head, which is rotated in the magnetic center at high frequency (typically several kHz) during the measurement at the “magic angle” (arctan√2, approximately 54.74°) with respect to the magnetic field lines in the stator of a turbine.
In many laboratories, NMR spectroscopy of both liquids and solids is performed with the same NMR system.
Due to the completely different shape and size of the sample tubes and spinners used in NMR spectroscopy of liquids, and of the rotors used in NMR spectroscopy of solids, it is necessary according to the prior art that the respective transport systems are also different.
A schematic arrangement for NMR spectroscopy of liquids according to the prior art known, for example, from Reference [1] is illustrated in FIG. 4. The HR (High Resolution)-NMR probe head (10) is installed in an NMR magnet (11) so that the magnetic field required for the measurement is present at the measurement site. By means of an HR-NMR transport system (12), the HR-NMR sample spinner (14), which is filled with the liquid to be examined and inserted into a spinner, is transported pneumatically as a whole to the measuring position (14a) to the HR-NMR probe head (10), and after the measurement is transported back to the starting position.
A schematic arrangement for NMR spectroscopy of solids according to the prior art is illustrated in FIG. 5. The MAS (magic angle spinning) probe head (16) is installed in an NMR magnet (11) so that the magnetic field required for the measurement is present at the measurement site. By means of an MAS rotor transport system (13), the rotor (5) filled with the substance to be examined is pneumatically transported to the measuring position (5a) of the MAS probe head (16), and after the measurement is transported back to the starting position. For the measurement, the rotor axis is tilted by the “magic angle.”
The disadvantage here is that two different transport systems (HR-NMR 12 and MAS rotor 13) and two types of automation devices for sequentially feeding a large number of samples have to be provided for an NMR system, and that when changing from NMR spectroscopy of liquids to NMR spectroscopy of solids and vice versa, complicated conversions of the transport system are necessary each time, which is particularly laborious if additional automation devices are also used, as described in Reference [2], for example.
A possible solution according to the prior art is described in Reference [3]. Here, the NMR MAS rotor (5) is not fed from above by a transport system, but, rather, is fed from below through the MAS probe head (16) so that the HR-NMR transport system (12) for HR-NMR sample spinners can remain stationary. However, the disadvantage of this solution is the significant space requirement within the MAS probe head (16).
It is therefore an object of the invention to be able to rapidly change from NMR spectroscopy of liquids to NMR spectroscopy of solids, and vice versa, without converting the transport system, but instead, only by exchanging the probe head. It is intended that in both cases the same transport system and in particular also the same automation devices for sequentially feeding a large number of samples can be used, without conversion, with existing NMR MAS probe heads as well as with MAS rotors.